Walgreens, already the largest drug retailing chain in the US, is to expand into the global marketplace with the takeover of Alliance Boots in the UK.

It may have work to do on its reputation among female consumers, however, as it has repeatedly come under fire from US reproductive health activists for not doing more to ensure individual pharmacists abide by federal laws to provide emergency contraception.

At a national level, Walgreens, which has thousands of stores across the US, complies with FDA's regulations on contraception and other healthcare provisions. But its name has become associated with a disturbing trend among pharmacists who have refused to provide over-the-counter emergency contraception to men buying it for their female partners.

The American Civil Liberties Union (ACLU) said they had received a number of complaints from men who have had their requests for emergency contraception refused by pharmacists in Walgreens.

The group complained to Walgreens several times in 2010, and received what they described as an "encouraging response" from the parent store, saying they had distributed a bulletin telling all its stores that emergency contraception can be sold to men and that a male customer need not be accompanied by a female customer. But since then, there have been other cases.

Brigitte Amiri, a senior legal attorney for the ACLU Foundation, said: "We've had a number of complaints, the most recent in Georgia in February. It is a cause for concern that it has happened again in a store in the south. We are still waiting for their response."

ACLU wrote to Walgreens in 2010 after stores in Texas and Mississippi refused to sell contraception to men. When one man who tried to buy contraception was refused, he complained to the store manager, only to find she stood by the pharmacist's decision.

He then received a call from the store manager apologising but saying the store had an "unwritten rule" not to give the drug to men because they might give it to an underage person. She then commented there had been news reports of people dropping the drug into women's drinks.

Amiri said that it seemed to be a problem with individual pharmacists in stores, because whenever they have taken it up at the corporate level, they have found Walgreens and other drug stores to have policies which comply with FDA guidelines.

In response to complaints from ACLU, Walgreens stores have launched investigations and then re-trained staff in accordance with the national policy.

"It's been a problem at the store level with individual employees. At the corporate level the have been very clear that their policy is to provide contraception in accordance with FDA guidelines to men and women aged 17 and over," Amiri said.

Amiri said it appeared to be a problem in most of the major drug stores in the US, including CVS, Rite Aid and Target, but most complaints had concerned Walgreens.

"We have seen it in different parts of the country, which makes me think there has been some advocacy group of pharmacists who don't believe in giving contraception, and individual pharmacists are using their personal beliefs to discriminate."

The FDA has approved emergency contraception for sale behind the pharmacy counter for men and women aged 17 and older.

Over the past year, the social change website Change.org has run a petition relating to the so-called "unwritten rule" cited by Walgreens stores in Texas.

Cristina Page has chronicled efforts to obstruct Americans' access to birth control,in her book on the war on contraception, How the Pro-Choice Movement Saved America.

Page said that although there are a handful of states that allow pharmacists to refuse to provide contraception, policies can be adopted that ensure patients are able to get their prescriptions for contraception while allowing for individual pharmacist's religious objections, such as having two pharmacists available.

"There is a disturbing trend with pharmacists pre-empting the healthcare decisions patients make with their doctors," said Page. "These pharmacists are imposing their religious views in other people's lives based on the scientifically inaccurate belief that contraception can cause an abortion and, as a result, is against their religious beliefs. All scientific evidence shows contraception has no abortifacient effect. But providing evidence to counter these beliefs appears to be futile"

Asked if drug stores were doing enough to stop individual pharmacists taking matters into their own hands, she said: "If even one instance happens when one patient is unable to get medication they need because of one person's specious beliefs, then not enough is being done. If something is over the counter, it's over the counter."